U.S. Pat. No. 5,799,548 to Brooks et al discloses two substantially parallel metal support plates having plastic gears rotatably supported therebetween. Each of the plastic gears is rotatably supported by its hub on two plastic fixed support studs with each extending from one of the two support plates.
A nominal clearance is provided between the outer surface of each of the two fixed support studs and the inner surface of the gear hub. As the nominal clearance between the outer surface of each of the two fixed support studs and the inner surface of the gear hub increases, the plastic gear is subjected to increased vibration or jitter (imprecise and wavering rotation). When the plastic gear is the output gear of a gear train connected to an input gear of a photoconductive drum of a laser printer for rotating the drum, this vibration or jitter creates vibrations in the drum to affect the print quality of the laser printer.
If the nominal clearance between the outer surface of each of the two fixed support studs and the inner surface of the gear hub is reduced towards zero to decrease the vibration or jitter and improve the print quality, binding of the gear hub on each of the two fixed support studs may occur. This is because the tolerances of the gear hub and each of the two fixed support studs can exceed the nominal clearance.
This binding of the gear hub on one or both of the two fixed support studs would increase the torque required to rotate the gear hub on the two fixed support studs. In addition to requiring an increase in the torque with a decrease in the nominal
clearance between the inner surface of the gear hub and the circumference of the fixed support studs, binding also causes excessive wear of the gear hub and the two fixed support studs. Binding also could cause seizing. Therefore, reducing the nominal clearance between the inner surface of the gear hub and the outer surface of each of the two fixed support studs by increasing the diameter of each of the two fixed support studs, for example, is not a solution to reducing jitter or vibration of the plastic gear so as to improve print quality of a laser printer having its photoconductive drum driven by a gear train.